1. Field of the Invention
This invention relates to a process of defrosting an evaporator of a refrigeration system used for refrigeration or as a heat pump, wherein the refrigerant circuit leading from the compressor to the condenser and from the latter through a throttle valve and the evaporator back to the compressor is altered and the refrigerant delivered by the compressor is supplied to the evaporator and caused to by-pass the condenser, the refrigerant is used as a heat source for a heat accumulator during normal operation and the heat accumulator is used as a heat source for the refrigerant during a defrosting operation. The invention relates also to a refrigerating system for carrying out that process.
2. Description of the Prior Art
For an operation of heat pumps using air as a source of energy, the evaporator must not be covered with ice, which would restrict the transfer of heat from the air to the refrigerant. For this reason the evaporator or evaporators must be defrosted from time to time when there is a danger of icing. This may be accomplished by expensive heating means supplied with extraneous energy and consisting particularly of electric resistance heaters, and it is also known for that purpose to reverse the heat pump cycle and to permit hot refrigerant vapor to flow directly into the evaporator. In that case the evaporator operates virtually as a condenser and the heat released by the condensation of the refrigerant vapor is used to defrost the evaporator. The thus condensed refrigerant is pressure-relieved in the throttle valve and then flows in the reversed direction of flow through the condenser proper of the heat pump; that condenser is now operated as an evaporator, and finally back to the compressor. The latter is operatively connected by means of a heat exchanger to a heating circuit and during the defrosting operation extracts from that heating circuit the heat required to evaporate said refrigerant. As a result, the heating system is cooled, which is most undesirable from the aspect of a conservation of energy, and the operation of the refrigerating system is rendered rather uneconomical.
In U.S. Pat. Nos. 3,838,582 and 2,641,908 it has already been proposed to supply heat from the refrigerant to a heat accumulator and to use the thus accumulated heat for defrosting. In those cases the heat accumulator closely succeeds the compressor so that defrosting is effected by superheat energy. That practice is also uneconomical and adds to the structural expenditure of the system owing to the high temperatures and pressures which are required.
East German Patent Specification No. 133,462 discloses a heat pump having a plurality of evaporators and adapted to defrost the evaporators by means of the residual heat content of the condensate leaving the condenser. For this purpose a part of that condensate, which is still warm, is passed through the evaporators in alternation in order to defrost the latter. In that case, the structural expenditure is relatively high and each evaporator cannot be completely defrosted unless the condensate has a relatively high temperature of about 50.degree. C. For this reason such heat pump cannot be used for low-temperature heating systems, such as floor heating systems, although heat pumps are particularly useful for that purpose in other respects.